Drill Design Research Articles

Fluid Design to Meet Reservoir Issues - A Process

Abstract As open hole completions, horizontal wells, multi-laterals, and underbalanced drilling become more common place, greater emphasis is being placed on the selection and design of drilling and completion fluids. The problem of assessing fluid compatibility with hydrocarbon reservoirs is ongoing and usually unique to each reservoir. This problem becomes most visible after resources have been expended to drill, with unsatisfactory results in productivity. The objective of this paper is to present a process designed to use the best available methodologies and laboratory techniques to assist in the design and selection of fluids which will be most compatible with the reservoir. Ultimately the goal is to drill zero skin wells. The process addresses fluid design issues from both a bridging or solid phase perspective and a liquid phase perspective. Optimization relative to design such as chemical selection and concentrations are an integral part of the process. Using this process will reduce uncertainty regarding fluid selection and the impact of the fluids on productivity. Ultimately it is meant to assist in both increasing well productivity and reducing the requirement for expensive stimulation. The process may lead to innovation, resulting in new systems or products. It may be applied when designing workover and completion fluids or for drill-in fluids including overbalanced or underbalanced applications. Introduction The potential to reduce wellbore productivity while conducting drilling completion and workover procedures has been addressed extensively in petroleum related literature. Productivity impairment was originally recognized in field cases where development wells produced only small volumes of fluid upon completion or where producing wells produced less after work-over procedures. In other instances, where drill stem tests taken while drilling deep wells indicated potentially good production from shallow zones, difficulty was experienced in attaining production from those zones which had remained in contact with drilling muds for an extended time(l). Investigations of specific damage mechanisms is an ongoing pursuit. Bates et al. discussed the influence of clay content on water conductivity of oil sands in 1946(2). Nowak et al. studied the effect of mud filtrates and mud particles on permeability in 1951(3). Various models which consider formation damage have quantifiable outputs such as Skin Effect(4), Productivity Index(5) and Formation Damage Index Number(6). Methods of preventing formation damage continue to be tested, developed, and documented. A greater percentage of wells are now designed as open hole completions, where perforating past the damaged zone is impractical. Consequently, sophistication in fluids testing procedures has increased and frequently operators test whole fluids against their rock. Often fluid samples are obtained from multiple sources. Return permeability tests(7) are regularly used to select the "best" fluid. Unfortunately, if an adequate candidate isn't found, the data are usually insufficient to redefine the direction testing should take. The process described herein helps to categorize and quantify discrete damage mechanisms. Fluid design is systematically optimized for all damage issues such that ultimately the fluid is compatible with the reservoir. In actual practice the first line of defense against formation impairment is to keep foreign fluids and solids out of the rock.

The Correlation Between the Cutting Fluid Pressure Distribution and the Topography of Tool Wear in BTA Drilling

This paper investigates experimentally the correlation between the cutting fluid pressure distribution in the bottom clearance (the space enclosed by the bottom of the hole being drilled from one side and the flanks of the drill head from the other) and the flank wear of BTA drills. Two types of BTA drills were studied representing two basic drill designs in the current use: single- and multi-edge drilling heads. Experiments included the study of the bottom clearance topology, the measurements of the cutting fluid pressure distribution in the bottom clearance, and the study of the tool wear topology. The results reveal the notable correlation between the cutting fluid pressure distribution in the bottom clearance and the topography of tool wear.

Development of curved helical micro-drill point technology for micro-hole drilling

At the present time micro-drills with planar point geometry are prevalent in industrial practice. Unfortunately, they possess a number of undesired characteristics and limitations that influence their performance in terms of hole quality and tool life. To resolve the problems of planar micro-drills, this paper focuses on issues related to micro-drill point geometry (including the flank and flute) and presents a framework for a technology, built around a computer integrated system, for the design, manufacture, and evaluation of drills in general and of a new generation of micro-drills with curved helical point and flute geometry in particular. It is expected that this technology will support the rapid development of new customized micro-drills to meet specific manufacturing requirements.

Integration of Old and New Measurements To Optimize Redevelopment of the Lower Lagunillas Reservoir of Bloque IV, Lake Maracaibo, Venezuela

Summary The Lower Lagunillas of Bloque IV of the Bachaquero field is a supergiant reservoir that has been in production since 1956. We have carried out a pilot reservoir characterization study in the central part of the field, in which we have integrated all the available data into three-dimensional (3D) reservoir simulation models whose purpose is to optimize redevelopment of the area with horizontal wells. An analysis of the history of production was undertaken to gain an insight into the reservoir dynamics. This analysis indicated the inefficiency of gas injection in providing pressure support to the pilot study area and demonstrated the presence of active aquifer encroachment from the south. Anomalies in production behavior and fluid characteristics indicate both lateral and vertical compartmentalization of the reservoir. We have integrated Fourier transform infrared (FTIR) measurements of mineralogy from old cores with a comprehensive logging suite in a new well to re-evaluate older, sparse logging suites. The application of a mineral-based log evaluation and high-resolution processing of the new logs has led to a significant increase in estimates of oil initially in place in the study area. We have used a novel approach to estimate permeability in all wells in the study area. Combining these new evaluations with a revised geological model enabled us to recognize 11 geological layers throughout the area. Formation pressure measurements confirm that partial barriers to vertical communication exist between most of these layers. Cased hole saturation measurements and historical production data indicate an uneven sweep of these layers, such that five layers contain bypassed oil that could be recovered by horizontal wells. We have constructed very detailed simulation models that describe the lateral and vertical variation in petrophysical properties of each of these layers. These models have been used to select the optimum locations for horizontal wells and to optimize their drilling sequence and design. It is estimated that each of these wells could recover 1 to 1.5 million stock-tank barrels (STB) within 5 years. The first well drilled as a result of this study has produced dry oil at rates up to 469 BOPD from a zone not previously considered as a pay zone.

Computer-Aided Modelling of the Fluting Process for Twist Drill Design and Manufacture

Computer-aided models of a typical flute grinder, incorporating both ‘forward’ and ‘backward’ analyses, are outlined and used to simulate the flute grinding process and study the intended or design flute profile of twist drills. Based on recommended wheel profile and flute grinder settings, the ‘forward’ analysis has shown that the generated lip flute profile closely approximated the ideal profile for straight lip production while the heel flute profile approximated a parabolic curve. Furthermore the flute profile was partly generated by the ‘envelope’ of the wheel profiles and partly by the locus of the point of discontinuity on the wheel profile. The effects of the wheel profile and machine settings on the generated flute profile have been studied. The ‘backward’ analysis, based on the ‘contact curve’ method, has shown that only portions of the required wheel profiles to generate the given ‘design’ drill flute profiles were physically feasible so that the generated flute profiles are only good approximations of the design flute profiles. The use of these computer models in drill design and manufacture are also discussed.

Formation-Damage Minimization for Drilling and Cementing Fluids

This article is a synopsis of paper SPE 38040, "Could Formation Damage Minimization Provide a Cost-Effective Integrated Approach for the Design of Drilling and Cementing Fluids?" by B. Vidick, SPE, Dowell, and P. Reid, SPE, Schlumberger, originally presented at the 1997 SPE Asia Pacific Oil and Gas Conference held in Kuala Lumpur, 14-16 April.

No-tillage seeding: science and practice

The why and what of no tillage the nature of risk in no tillage slot shape and openers the role of slot cover drilling into dry soils drilling into wet soils seed metering and placement fertilizer placement effects residue handling by openers, drills and planters pasture renewal and renovation no-tillage drill and planter design managing a no-tillage seeding system techniques and procedures for developments.

Technical Considerations In Powered Instrumentation

This article reviews some of the technical engineering aspects of the soft-tissue shavers and bone-cutting drills. An improved understanding of these principles may allow the practicing surgeon to optimize the desired aggressiveness and precision of the instrument in his or her hands. Powered instrumentation has found extended uses beyond sinus disease, such as submental lipectomy (soft-tissue shaver) and modifying the bony nasal dorsum (bone cutting bur). Changes in drill design to address these and other surgical situations are discussed.

Applying the finite element method to drill design based on drill deformations

The design of the twist drill with special cross-sectional shape using the finite element method based upon drill deformations was presented in this paper. In order to improve the unfavorable distribution of the total orthogonal rake angle along the primary cutting edge of a thick web drill, a thick web drill with curved primary cutting edges was devised. The profile of the curved primary cutting edge was mathematically determined by changing the distribution of the tool orthogonal rake angle along the primary cutting edge. A three-dimensional finite element analysis based upon the drill deformations was applied to obtain the “secondary” flute shape and to specify the web thickness, the helix angle, and the flute length. The effect of these geometric [arameters on drill deformations was also investigated. Experiments were conducted to evaluate the drill's cutting performance. Experimental results indicated that the thick web drill with curved primary cutting edges was effective in reducing the thrust force, the torque, and the tool wear, a strength that definitely provided a better cutting drill and longer tool life for drilling the JIS S50C heat-treated steel.

Predictive Force Models for Point-Thinned and Circular Centre Edge Twist Drill Designs

The geometry and specification of point thinned general purpose and facet point drills as well as the patented ‘circular centre edge’ twist drill design are studied and used to develop predictive mechanics of cutting models for the thrusts and torques for these drill designs. It is shown that the three designs involve point thinning, to improve the rake angle and cutting action at the chisel edge, with the circular centre edge drill being a variation of the point thinned facet point drill. The predictive models have been numerically and experimentally tested. While these drill designs substantially reduce the thrust force when compared to unthinned drills the difference in the forces for the three designs are minimal when compared on a fair basis. The importance of geometry and force modelling in assessing drill designs is highlighted in this work.

Positioning of the tibial tunnel for anterior cruciate ligament reconstruction.

Two mechanisms of unintentional anterior tibial tunnel axis shift can occur despite accurate placement of the guide wire within the proximal tibia. The first results from using a short-block reamer head joined to a shaft of smaller diameter. If the tibial tunnel is drilled obliquely, it is possible for the reamer head to displace anteriorly in the knee joint before completion of the posterior portion of the tibial tunnel. The second mechanism of anterior shift involves using two sequential drills to create the tibial tunnel. To delineate the causes of this unwanted shift, cadaveric studies and special roentgenographic studies were undertaken. Results demonstrated that the shift is related directly to the presence of high-density bone in the tibial plateau. In an effort to minimize this effect, various drill designs were tested, and it was determined that a drill-head length of 25 mm was most effective at reducing the shift without sacrificing the freedom of movement necessary to obtain precise endosteal placement of the femoral tunnel. Along with these experimental studies, a retrospective 7-year review of anterior cruciate ligament (ACL) reconstruction failures was performed to assess the clinical significance of inadvertent anterior positioning of the tibial tunnel.

A Novel Approach to the Design of Self-Piloting Drills With External Chip Removal, Part 1: Geometry of the Cutting Tip and Grinding Process

The performance of a self-piloting drill with external chip removal is affected by the geometry of its cutting tip. A comprehensive analysis of the cutting tip geometry and its influence on the drill performance is made. This subject is treated in two parts. In Part 1, the cutting tip geometry is analyzed. Special attention is given to the flank planes and a novel approach to the design of the drill was developed. By this approach the drill flank planes are located with minimum offset of the supporting pads’ faces relative to the plane of the drill corner’s rotation. Since several important drill angles are defined, the analysis is extended to cover the grinding process. The experimental comparison between the ordinary and newly designed self-piloting drills with external chip removal is also made to show the advantages of the latter.

A Novel Approach to the Design of Self-Piloting Drills With External Chip Removal, Part 2: Bottom Clearance Topology and Experimental Results

In the first part of this paper, geometrical relations were formulated to describe the geometry of a self-piloting drill with external chip removal. A novel approach to the design of the cutting tip was proposed and an experimental comparison between conventional and newly designed drills was made. In deep hole drilling, after the tool and the machine, the most important component is the coolant. It is important that the coolant be distributed uniformly within the machining zone to improve chip removal, lubrication and cooling. Thus, in this paper, the coolant flow in the limited space between the drill flanks and the bottom of the hole being drilled (called “bottom clearance”) is emphasized. Experimental investigations were done by using a specially designed workpiece which enables continuous monitoring of coolant flow and pressure distribution in the machining zone. The investigation shows that the newly designed drill is characterized by a significantly better coolant distribution in the bottom clearance resulting in an increase in tool life and better chip removal conditions.

Large-scale mineral potential estimation for blind precious metal ore bodies

Conventional evaluation of quantitative mineral potential has focused on target selection at small scales. Mapping at small scales usually results in large-area targets, which may be suitable for grass-roots exploration or regional evaluation of potential. Unfortunately, the estimates in small-scale exploration are commonly associated with large uncertainties. Large-scale estimation is used for optimal in-fill drilling design and step-out drilling target selection. In-fill drilling helps to confirm ore-grade continuities and translate a portion of geological resources into minable reserves, whereas step-out target estimation is useful for finding new orebodies in the vicinity of known ore deposits. Both of these processes are necessary for mine development and production planning. A comprehensive methodology is proposed here, particularly for large-scale mineral exploration. The central information synthesizer is canonical or indicator favorability analysis. A case study is presented to demonstrate the methodology for large-scale target selection. The study involves a gold-mining district where step-out drilling targets are being sought to expand the resource base. Several drilling targets were delineated in the study region. Two of them were tested through surface sampling with positive results.

An investigation of the cutting fluid flow in self-piloting drills

The conditions of the coolant flow through the inlet annular channels, machining zone and outlet channels of self-piloting drills were investigated. Experiments were performed on B.T.A. and Ejector drills to determine the influence of the drill design parameters on the flow parameters. The influence of the inlet channel's clearance and eccentricity on the pressure distribution and energy loss was analytically examined. Experimental investigations of the static and dynamic pressure distribution of the cutting fluid in the machining zone were performed with different drill heads. Conditions for reliable chip removal from the machining zone and the boring bar were defined. The results obtained constitute a reference for designers of self-piloting drills and drilling processes.

CAD Applied to Twist Drills

A computer aided design (CAD) modeller has been developed to facilitate the design of twist drills. A feature of the system is its ability to accept both the theoretical mathematical parameters used by drill theorists and those parameters used as standard nomenclature in the drill industry. Differences between the theoretical and ‘real’ drills are accounted for. The program presents a variety of views of the three-dimensional drill model and provides relevant numerical information. The CAD modeller is a platform for a greater computer aided engineering (CAE) system, which is involved from the initial design stage through to manufacture.

Determination of optimal air flow rate in air drilling

Optimal design of any drilling program requires good knowledge of wellbore hydraulics. Established techniques are available for formulating some understanding of the associated wellbore hydraulics for conventional mud drilling, but this is not the case for air drilling. The wellbore hydraulics of air drilling present distinctly different problems from those associated with mud drilling. A systematic study of these problems, especially utilizing fundamental approaches, is lacking. This study addresses this problem using a fundamental, hydrodynamic multiphase flow model for air drilling. Extensive parametric analysis of the system is performed to validate the viability of the model as a predictive tool. The model is demonstrably capable of predicting the pressure-drop profile in the annulus and the optimal lifting velocity, an essential ingredient in the optimal design of air drilling. The results demonstrate the ability of the model to predict a number of phenomena that are associated with lifting cuttings from the hole during air drilling. The model possesses scale-up capability.

On the design of deep-hole drills with non-traditional ejectors

Abstract This work deals with the development of design criteria for deep-hole drills with non-traditional ejectors of circular and plain type. An analytical method for design on non-traditional ejectors with circular jet was developed. The experimental investigation of the developed method was found suitable for the design of single lip non-traditional ejector gundrills of bigger diameter. For smaller diameter drills the results were not satisfactory. For smaller diameter size gundrills the equations analytically developed were modified to suit the experimental results. Further investigation of these modified equations found them to be appropriate. In the case of plain type ejectors, the design methods were developed based on experimental results since this type of ejector does not lend itself easily to theoretical analysis.

Percussive energy transfer in pneumatic top hammer rock drills

ABSTRACT A mathematical model of pneumatic roll drills is introduced. This model takes into account the local deformation of impact ends of piston and shank adapter. For this model, there is a good agreement between theoretical and experimental results. Two dimensionless parameters related to the mass of piston, the local deformation of impact ends, characteristic impedance of rod, and force-penetration characteristic at bit-rock interface, are introduced. The analysis indicates that the checking of these dimensionless parameters and letting them be in certain ranges are helpful for the design of pneumatic rock drills to achieve high efficiency of energy transfer.

Design of drilling and blasting subsystems — a rock mass classification approach : Ghose, A K Proc International Symposium on Mine Planning and Equipment Selection, Calgary, 3–4 November 1988P335–340. Publ Rotterdam: A A Balkema, 1988

Design of drilling and blasting subsystems — a rock mass classification approach : Ghose, A K Proc International Symposium on Mine Planning and Equipment Selection, Calgary, 3–4 November 1988P335–340. Publ Rotterdam: A A Balkema, 1988